Windshield antenna

ABSTRACT

A vehicle windscreen is provided with electrical antenna conductors in the form of a row of open loops connected to at least one straight horizontal arm. The loops lie in an area corresponding to the rear view mirror position. In situ in a vehicle the loops do not project below the lower edge of the rear view mirror and the loop do not project beyond the lateral edge of the mirror. Between three and 12 loops may be provided and they may be connected to a second horizontal conductor arm. A vertical conducting arm may also be connected to the row of loops. The conductors may lie on the inner surface of the windscreen.

Cleminson et al.

1451 Aug. 27, 1974 WINDSHIELD ANTENNA Inventors: Frederick AntonyCleminson, London; Brian Arthur Ariss, Birmingham, both of EnglandAssignee: Triplex Safety Glass Company Limited, London, England Filed:Nov. 13, 1973 Appl. No.: 415,487

Foreign Application Priority Data Nov. 14, 1972 Great Britain 52577/72us. or 343/713, 343/720 Int. Cl. H01q 1/32 Field of Search 343/711, 712,713, 720

Primary Examiner-Eli Lieberman Attorney, Agent, or Firm-Sughrue,Rothwell, Mion,

Zinn & Macpeak ABSTRACT A vehicle windscreen is provided with electricalantenna conductors in the form of a row of open loops connected to atleast one straight horizontal arm. The loops lie in an areacorresponding to the rear view mirror position. In situ in a vehicle theloops do not project below the lower edge of the rear view mirror andthe loop do not project beyond the lateral edge of the mirror. Betweenthree and 12 loops may be provided and they may be connected to a secondhorizontal conductor arm. A vertical conducting arm may also beconnected to the row of loops. The conductors may lie on the innersurface of the windscreen.

l5 Clains, 6 Drawing Figures E y-i- WINDSHIELD ANTENNA BACKGROUND OF THEINVENTION The invention relates to vehicle windscreens and in particularto a vehicle windscreen including electrical antenna conductors.

Vehicle windscreens are known which are provided with electrical antennaconductors. Some difficulties have arisen in arranging the conductors soas to provide sufficient signal strength for a radio receiver whileavoiding undesirable obstruction of vision through the windscreen.

It is an object of the present invention to provide an improvedwindscreen incorporating electrical antenna conductors.

SUMMARY OF THE INVENTION The present invention provides a vehiclewindscreen provided with electrical antenna conductors, said conductorsincluding a plurality of open loops located in the area corresponding tothe rear view mirror position, said loops being joined in succession toform a row of loops extending along an upper part of the windscreen andspaced from the upper edge of the windscreen and at least one straighthorizontal arm being connected to one end of the row of loops alsoextending along the upper part of the windscreen, the loops forming theantenna being located in the area behind the rear view mirror positionso that the loops do not project substantially beyond the lateral edgesof said area andthe height of the loops in the row being such that theydo not project substantially below the lower edge of the said area.

Such an arrangement of antenna conductors enables the aerial to providesufficient signal strength for an AM radio receiver and the loops do notproject sufficiently far down the windscreen to interfere with visionthrough the windscreen.

All the loops forming the antenna are located in the area correspondingto the rear view mirror position so that the loops do not projectsubstantially beyond the lateral edges of the rear view mirror. Thisreduces interferance with vision to a minimum.

Preferably the antenna conductors comprise from three to 12 loops and insome cases from six to 12 loops. Preferably the loops are not less than1 inch high. In this way, satisfactory signal strength may be provided.

Preferably the length of the row of loops is greater than the height ofthe loops. Such an arrangement is of practical convenience in that rearview mirrors normally have greater width than depth. In general,allowing for the variation in size and position of rear view mirrors theloops lie within an area 9 inches wide by 4 inches deep at the maximumand spaced from the upper edge of the windscreen by a distance notgreater than 3 inches. In some cases two straight horizontal arms may beprovided, one at each end of the row of loops. Additionally, a straightvertical arm may be connected tothe row of loops.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a vehicle windscreen witha known T- shaped aerial, not embodying the present invention, FIG. 2shows a further embodiment of the invention in which a single horizontalarm is added to the row of loops,

FIG. 3 shows a further embodiment of the invention in which'twohorizontal arms are connected to the row of loops,

FIG. 4 shows a further embodiment of the invention in which the antennaconductors consist of a row of loops together with one horizontal armand one vertical arm,

FIG.'5 shows a further embodiment of the invention in which twohorizontal arms and one vertical arm are added to the row of loops, and

FIG. 6 shows schematically a vehicle incorporating a windscreenembodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG.l, a vehicle windscreen11 is shown with a known aerial arrangement for a radio receiver. Theaerial consists of two horizontal conducting arms 12 and 13 joined to avertical arm 14 having a suitable termination 15 at its lower end foruse in connecting the aerial to a radio receiver.

FIGS. 2 to 5 show various alternative embodiments of the presentinvention which all differ from the arrangement shown in FIG. 1 in thatthe antenna conductors include as well as a horizontal arm 18, aplurality of open loops joined in succession to form a row of loops inthe upper central part of the windscreen and in the area normally behinda rear view mirror. In each of the examples in FIGS. 2 to 5, the row ofloops 16 extends horizontally along the upper part of the windscreen 11so that the upper edge of the loops is spaced from the top of thewindscreen and the lower edge of the loops does not project below thelower edge of the rear view mirror position in the motor vehicle. Ineach of FIGS. 2 to 5, the position of the rear view mirror is shownby-broken lines 17. In FIG. 2, a single straight horizontal arm 18 isconnected to one end of the row of loops and extends parallel to andspaced from the upper edge of the windscreen. A suitable termination 15is provided at the end of the arm 18 remote from the row of loops 16.Alternatively the termination 15 may be provided at the free end of therow of loops 16. Such an alternative is marked 15a in FIG. 2. In FIG. 3,a sec- 0nd straight horizontal arm 19 is connected to the other end ofthe row of loops 16. The examples shown in FIGS. 4 and 5 are generallysimilar to those shown in FIGS. 2 and 3 except that a vertical arm 14 isin each case connected to the row of loops 16. The upper end of thevertical arm is in each case connected to the row of loops mid-way alongthe row of loops. Although in FIGS. 4 and 5 the termination 15 is shownat the end of the horizontal arm 18, it may alternatively be provided atthe free end of the row of loops 16 (FIG. 4) or at the end of the otherhorizontal arm (FIG. 5) or at the bottom of the vertical arm (FIGS. 4and 5). Alternatively in all the arrangements of FIGS. 2, 3, 4 and 5 thetermination 15 may be provided at a point intermediate the ends of therow of loops 16, preferably at the centre of the row of loops 16, asmarked 15b in FIG.

In each of the examples shown in FIGS. 2 to 5, the loops 16 all lie in asingle plane with each loop consisting of a rounded S-shaped portionlying on its side. The number and size of loops may be varied to suitthe vehicle and radio receiver being used. The shape of the loops mayalso be varied, for example the S-shape could be squared up or astraight sided zig-zag could be inches and in each case the mirror issituated centrally 1 across the width of the windscreen.

taken at a location where the signals were comparatively very strong andwith the antenna coupled to the voltmeter by 6 inches of low loss cable.Example 1 given in the Table is the known configuration of aerial shownin FIG. 1 of the accompanying drawings. Examples 2 to'10 show variousexamples in accordance with the present invention, in each case theheight of the loops was 3 inches and the length of the row of loops was6 inches.

In the various examples 2 to 10, the number of loops, height of loopsand length of row of loops was varied.

In order that the loops 16 do not project substantially beyond thelateral edges or below the lower edge of the rear view mirror, the loopswill in general lie within an area not more than 9 inches wide by 4inches deep, the

upper edges of the loops being spaced up to 3 inches 30 from the top ofthe windscreen. The actual area taken up by the loops on any particularwindscreen will however be determined by the size and position of therear view mirror to be fitted. The length of the horizontal arms 18 and19 and the vertical arm 14 should be as long as is possible within theconfines of the windscreen, but'the arms require to be terminated atleast 2 inches from the edge of the windscreen.

The following Table 2 gives the relative signal strengths achieved withdifferent configurations of aerial. The Table gives the signal strengthin millivolts as measured with a radio frequency voltmeter of theheterodyne type for the AM. transmissions of BBC Radio TABLE 2 SignalNumber Arranged Terminal Strength 0 of as Connection Millivolts Exampleloops shown in at end of A.M. Radio 2 1 known T vertical 23.0

aerial arm FIG. l v v 2 6 FIG. 2 horizontal 21.0

' arm 3 8 FIG. 2 horizontal 21.4 I I arm 4 10 FIG. 2 horizontal 21.6

. .3791. a w 5 12 FIG. 2 horizontal 20.6

e arm 6 3 FIG. 3 horizontal 19.0

arm 7 6 FIG. 3 horizontal 23.0

arm I 8 12 FIG. 3 horizontal 21.0

arm 9 3 FIG. 4 vertical 21.5

arm 10 3 FIG. 5 vertical 24.5

arm

2 at a frequency of 0.20 MHz. The measurements were Furthermore, theexamples covered the different arrangements shown in FIGS. 2 to 5 andthe location of the terminal connection 15 differed in the variousexamples.

In the above examples, it is considered that the signal strengthsrepresent good reception in being greater than a value of 19.0millivolts.

Overall it is preferred to use from three to 12 loops not less than 1inch in height.

In the case of a laminated windscreen, the antenna conductors may bepositioned in one of the glass/interlayer interfaces or preferably onone of the exposed glass surfaces, particularly that which will beinside the vehicle. In the case of a windscreen formed from a sin- 0 glesheet of toughened glass, the antenna conductors t are preferablypositioned on the surface that is to be inside the motor vehicle. It ishowever possible to locate the conductors on the outer surface.

The conductors may be wire or a deposit of some conducting materialalthough wire can only be used with a laminated windscreen when it willusually be positioned in one of the glass/interlayer interfaces. Thewire 'may for example be 24 gauge copper wire, that is wire having adiameter of 22 thousandths of an inch. If a conducting deposit is used,this may be applied by a silk screen printing process using an ink whichis fired onto the glass surface and preferably that surface which willlie inside the vehicle. The ink may contain a silver compound and a lowmelting point glass frit as referred to in British Pat. No. 1145367.Suitable commercially available inks are supplied for example by Degussaunder thereference number 314E and by DuPont under reference numbers EX8438R and EX 8439R and EX 8448R. Alternatively an ink formed of a silverI oxide organic silver salt complex supplied by Englehard may be used.The width of the printed line is in the region of 0.4 millimetres andmay for example be 0.35 millimetres. Firing of the ink occurs duringheating the glass for bending and toughening when the, glass is atapproximately 650C.

FIG. 6 shows the use of the invention in a motor car 20. The car 20 hasa windscreen 11' incorporating antenna conductors having the generalarrangement described with reference to FIG. 3. The loops l6 lie whollybehind a rear view mirror 21 which is fixed adjacent the upper centralpart of the windscreen. The terminal is connected by a suitableconductor to an A.M..radio receiver mounted within the vehicle.

The invention is not limited to the details of the foregoing examples.

We claim:

1. A vehicle windscreen provided with electrical antenna conductors,said conductors including a plurality of open loops located in the areacorresponding to the rear view mirror position, said loops being joinedin succession to form a row of loops extending along an upper part ofthe windscreen and spaced from the upper edge of the windscreen and atleast one straight horizontal arm being connected to one end of the rowof loops also extending along the upper part of the windscreen, theloops forming the antenna being located in the area behind the rear viewmirror position so that the loops do not project substantially beyondthe lateral edges of said area and the height of the loops in the rowbeing such that they do not project substantially below the lower edgeof the said area.

2. A vehicle windscreen according to claim 1, in which the antennaconductors comprise from six to 12 loops.

3. A vehicle windscreen according to claim 1, in which a second straightarm is connected to the loops and the antenna conductors include fromthree to 12 loops.

4. A vehicle windscreen according to claim 1, in which the loops are notless than 1 inch high' 5. A vehicle windscreen according to claim 1, inwhich the length of the row of loops is greater than the height of theloops.

6. A vehicle windscreen according to claim 1, in which the loops liewithin an area 9 inches wide by 4 inches deep, the area lying centrallyacross the width of the windscreen.

7. A vehicle windscreen according to claim 6, in which the upper edge ofthe loops is spaced from the upper edge of the windscreen by a distancenot greater than 3 inches.

8. A vehicle windscreen according to claim 1, in which a straightvertical arm is connected to the row of loops.

9. A vehicle windscreen according to claim 1, including two straighthorizontal arms one connected to each end of the row of loops.

10. A vehicle windscreen according to claim 1, in which the end of anarm remote from the row of loops is used as a terminal for connectingthe antenna to a receiving circuit.

11. A vehicle windscreen according to claim 1, in which a connectingterminal is provided at a free end of the row of loops.

12. A vehicle windscreen according to claim 1, in which a connectingterminal is provided at a point interrnediate the ends of the row ofloops.

13. A vehicle windscreen according to claim 1, in which the conductorsare positioned on the inner surface of the windscreen.

14. In a motor vehicle a windscreen according to claim 1, together witha rear view mirror, the loops in the antenna conductors being located inthe area lying behind the rear view mirror as seen by the driver.

15. A vehicle having a windscreen as claimed in claim 1, together with arear view mirror, the loops in the antenna conductors being located inthe area lying behind the rear view mirror as seen by the driver.

1. A vehicle windscreen provided with electrical antenna conductors,said conductors including a plurality of open loops located in the areacorresponding to the rear view mirror position, said loops being joinedin succession to form a row of loops extending along an upper part ofthe windscreen and spaced from the upper edge of the windscreen and atleast one straight horizontal arm being connected to one end of the rowof loops also extending along the upper part of the windscreen, theloops forming the antenna being located in the area behind the rear viewmirror position so that the loops do not project substantially beyondthe lateral edges of said area and the height of the loops in the rowbeing such that they do not project substantially below the lower edgeof the said area.
 2. A vehicle windscreen according to claim 1, in whichthe antenna conductors comprise from six to 12 loops.
 3. A vehiclewindscreen according to claim 1, in which a second straight arm isconnected to the loops and the antenna conductors include from three to12 loops.
 4. A vehicle windscreen according to claim 1, in which theloops are not less than 1 inch high.
 5. A vehicle windscreen accordingto claim 1, in which the length of the row of loops is greater than theheight of the loops.
 6. A vehicle windscreen according to claim 1, inwhich the loops lie within an area 9 inches wide by 4 inches deep, thearea lying centrally across the width of the windscreen.
 7. A vehiclewindscreen according to claim 6, in which the upper edge of the loops isspaced from the upper edge of the windscreen by a distance not greaterthan 3 inches.
 8. A vehicle windscreen according to claim 1, in which astraight vertical arm is connected to the row of loops.
 9. A vehiclewindscreen according to claim 1, including two straight horizontal armsone connected to each end of the row of loops.
 10. A vehicle windscreenaccording to claim 1, in which the end of an arm remote from the row ofloops is used as a terminal for connecting the antenna to a receivingcircuit.
 11. A vehicle windscreen according to claim 1, in which aconnecting terminal is provided at a free end of the row of loops.
 12. Avehicle windscrEen according to claim 1, in which a connecting terminalis provided at a point intermediate the ends of the row of loops.
 13. Avehicle windscreen according to claim 1, in which the conductors arepositioned on the inner surface of the windscreen.
 14. In a motorvehicle a windscreen according to claim 1, together with a rear viewmirror, the loops in the antenna conductors being located in the arealying behind the rear view mirror as seen by the driver.
 15. A vehiclehaving a windscreen as claimed in claim 1, together with a rear viewmirror, the loops in the antenna conductors being located in the arealying behind the rear view mirror as seen by the driver.